Text-to-speech from media content item snippets

ABSTRACT

A text-to-speech engine creates audio output that includes synthesized speech and one or more media content item snippets. The input text is obtained and partitioned into text sets. A track having lyrics that match a part of one of the text sets is identified. The location of the track&#39;s audio that contains the lyric is extracted based on forced alignment data. The extracted audio is combined with synthesized speech corresponding to the remainder of the input text to form audio output.

TECHNICAL FIELD

The present disclosure relates to technical solutions for text-to-speechsystems.

BACKGROUND

Text-to-speech systems (often abbreviated as TTS systems) convert textinput into an audio output, typically the audio output is designed tomimic a human speaking text. Text-to-speech systems play a significantfunction in utterance-based human-machine interfaces. Many devices usetext-to-speech systems to give voice to virtual assistants (e.g., theSIRI virtual assistant by APPLE, the CORTANA virtual assistant byMICROSOFT, GOOGLE ASSISTANT by GOOGLE, and the AMAZON ALEXA virtualassistant by AMAZON), such as those operating on phones and smartspeaker systems.

One technique that text-to-speech systems use to produce speech outputincludes determining a phoneme sequence from text. The phoneme sequenceis then converted into synthesizer data, which is used by a speechsynthesizer to produce output waveforms representative of the text.Improvements to text-to-speech systems can have correspondingimprovements in the ability of a human-machine interface (HMI) tointeract with users, such as by improving the expressiveness of the HMI.

US 2007/0055527 describes a voice synthesis system that converts a textcoming from a client apparatus into voices by analyzing the text. Thesystem has a background sound mixer that mixes background sound withsynthesized voices and a modulator for imparting sound-modulation effectto the synthesized voices.

SUMMARY

The present disclosure provides methods, apparatuses, andcomputer-readable products for generating audio output from text input.

In an example, there is a system providing text-to-speech functionality.The system includes a forced alignment data store having stored thereonforced alignment data for tracks and a combining engine. The combiningengine obtains input text; portions the input text into a first text setand a second text set; identifies a first track having first tracklyrics that include the first text set; identifies, using the forcedalignment data, a first audio location of the first track correspondingto the first text set; creates a first audio snippet containing thefirst audio location; using a speech synthesizer, creates a synthesizedutterance based on the second text set; combine the first audio snippetand the synthesized utterance to form combined audio; and provides anaudio output that includes the combined audio.

In some examples, the forced alignment data describes alignment betweenaudio data of the tracks and lyrics data of the tracks. In someexamples, the forced alignment data describes, for each of the tracks,lyrics data and time data of where lyrics occur in the audio data. Insome examples, the input text has a third text, and the combining engineis further configured to identify a second track based on the secondtrack having second track lyrics containing the third text set; andcreate a second audio snippet from the second track based on the thirdtext set. In some examples the combined audio further includes thesecond audio snippet. In some examples, identifying the second track isfurther based on audio characteristics of the first track and the secondtrack.

In some examples, identifying the second track includes selecting thesecond track based on similarities in musical style between the firsttrack and the second track. In some examples, the similarities inmusical style between the first track and the second track is determinedbased on a distance between the two tracks in vector space. In someexamples, the system further includes a forced alignment engine foraligning input track audio and input track lyrics. In some examples, theforced alignment engine is configured to find a Viterbi path through theinput track lyrics and the input track audio under an acoustic model. Insome examples, the forced alignment engine is configured to align theinput track lyrics and input track audio on a line-by-line basis. Insome examples, the forced alignment engine is configured to: receive athird track having track metadata; receive third track lyrics associatedwith the third track; select an acoustic model from an acoustic modeldata store based on the track metadata; using the acoustic model,generate third-track forced alignment data that aligns audio data of thethird track and the third track lyrics; and add the third-track forcedalignment data to the forced alignment data store. In some examples, thecombining engine is further configured to determine a quality describedin the input text, and identifying the first track is based at least inpart on the quality. In some examples, the quality is a music genre ormusic artist.

In an examples, a method performs: obtaining input text; portioning theinput text into a first text set and a second text set; determine aquality described in the first text set; identifying a first track basedon: the first track having first track lyrics that include the firsttext set; and the first track having the quality; identifying, usingforced alignment data, a first audio location of the first trackcorresponding to the first text set; creating a first audio snippetcontaining the first audio location; using a speech synthesizer,creating a synthesized utterance based on the second text set; combiningthe first audio snippet and the synthesized utterance to form combinedaudio; and providing an audio output that includes the combined audio.

In an example, the input text further has a third text set; and themethod further includes identifying a second track based on the secondtrack having second track lyrics containing the third text set based onsimilarities in musical style between the first track and the secondtrack; and creating a second audio snippet from the second track basedon the second text set. The combined audio further includes the secondaudio snippet.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present disclosure are apparent fromthe detailed description set forth below when taken in conjunction withthe following drawings.

FIG. 1 illustrates an example system that provides audio output usingtext-to-speech functionality according to an example embodiment of thepresent invention.

FIG. 2, which is made up of FIG. 2A and FIG. 2B, illustrates a processfor generating an audio output from input text according to an exampleembodiment of the present invention.

FIG. 3 illustrates a process for creating forced alignment dataaccording to an example embodiment of the present invention.

FIG. 4 illustrates an example visual representation of forced alignmentdata according to an example embodiment of the present invention.

FIG. 5 illustrates an example use of a system for producing an audiooutput according to an example embodiment of the present invention.

DETAILED DESCRIPTION

The example embodiments presented herein are directed to systems,methods, and non-transitory computer-readable medium products forgenerating audio output from text input. In many examples, the audiooutput is formed from a combination of one or more audio snippets, suchas audio snippets taken from tracks or other media content items. Wherethe audio snippets are taken from copyrighted media content items, theaudio snippets can used in accordance with relevant permission orlicense from the rights holder. In examples, the selection of tracks isperformed as a selection of a plurality of tracks that have beenlicensed or are already available for this purpose. For ease ofunderstanding, many example aspects of the embodiments described hereinare described in relation to tracks. This description is not intended tolimit the application of the example embodiments presented herein. Infact, after reading the following description, it will be apparent toone skilled in the relevant art(s) how to implement the followingexample embodiments in alternative embodiments (e.g., involving othertypes of media content items).

A track is an audio recording. Typically the audio recording is arecording of a piece music (e.g., a song). Tracks are often associatedwith lyrics and metadata. Lyrics refer to vocalized content of thetracks. Most commonly, the vocalized content corresponds to the words ofthe track, which are typically sung, spoken, or rapped. Metadata is dataabout data. With respect to media content, metadata is data thatdescribes information about the media content item and/or the mediacontent itself. For example, with regard to a track metadata, themetadata can contain information such as track length, track identifier(e.g., a unique identifier of the track), and track location (e.g.,where it is stored). Media content can be described according tomultiple facets. Such facets can be stored in a data store.

Facets (also sometimes referred to as descriptive facets) describeattributes of the media content. The list of facets is innumerable andincludes, for example: genre, locale, mood, opinion, instrumentation,style, time period, era/epoch, recording label, organizational, socialsignaling, musical setup, main instruments, variant, dynamics, tempo,metric, situation, character, language, rhythm and popularity.Multifaceted descriptions have been used for media content browsing andrecommendation. In example, a facet expressed as a key-value pairbetween a facet type and one or more facet values, such as: {tempo: 60bpm} or {genre: rock,blues}. A media content item is an item of mediacontent, including audio, video, or other types of media content, whichmay be stored in any format suitable for storing media content.Non-limiting examples of media content items include tracks, music,albums, audiobooks, music videos, movies, television episodes, podcasts,other types of audio or video content, and portions or combinationsthereof. Media content items often have vocalized content. As describedabove, the vocalized content of tracks is expressed as lyrics. Whileexamples herein are primarily explained in relation to lyrics, othercontent can be used. For instance, where a television show or podcastmedia content item is used, a transcript of the media content item isused instead of lyrics. Further, in some examples, non-lyrical musiccontent of the track can be used, such as instrumental passages denotedby sheet music, tabs, or another representation.

Disclosed examples include a new form of text-to-speech system thatincorporates snippets of media content items (e.g., music tracks) intospeech output, thereby improving the expressiveness of an HMI that usesthe new text-to-speech system. In an example, the text-to-speech systemcombines snippets of music tracks to form the “voice” of a virtualassistant. For instance, rather than verbalizing the text “now playingyour rock and roll playlist” using a traditional text-to-speech system,the text-to-speech engine combines snippets of tracks where theconstituent words and phrases are sung, spoken, or rapped.

Example aspects of the present invention provide new technical solutionsfor managing and combining one or more snippets from one or more tracksto form an audio output based on text input. Traditional text-to-speechsystems lack such a feature. In an example embodiment, a text-to-speechsystem includes a forced alignment data store and a combining engine.The forced alignment data store has forced alignment data describingalignment between audio of tracks and lyrics of tracks. For instance,for each respective track, the forced alignment data includes timestampsof where each lyric of the respective track is located within therespective track (e.g., where it can be heard in the audio of therespective track). A timestamp is data describing time, such as a pointin time relative to the start of a track (e.g., a number of seconds).The forced alignment data can include multiple timestamps, such as astart time and an end time in the track for each lyric of the track.

The combining engine creates audio output of the text-to-speech systemby combining audio snippets from two or more sources (e.g., sampledportions from two or more media content items). In an example, thecombining engine obtains input text having first text set and a secondtext set. The combining engine identifies a first track having lyricscontaining the first text set. The combining engine then uses the forcedalignment data to identify a first audio location of the first trackthat corresponds to the first text set. An audio snippet is generatedfrom the first track that includes the first audio location. In anexample, the text-to-speech system uses a speech synthesizer to vocalizethe second text set. In another example, combining engine identifies asecond track based on the second track having the second text set in itslyrics and also based on similarities in the audio characteristics ofboth tracks (e.g., characteristics that contribute to a good transitionbetween the tracks, such as key, beats, and tone, among othercharacteristics). For instance, the identification is based onsimilarities in musical style between the first and second tracks. Forinstance, the similarities of the tracks is determined based on adistance between the two tracks in vector space. A second audio snippetis created from the second track based on the second text set. Thecombining engine combines the first audio snippet and the second audiosnippet to form combined audio. In turn, the combined audio is providedas output.

In an example, the text-to-speech system further determines a qualitydescribed in the input text. The quality is an attribute of the text.The quality can be used for identifying tracks based on their similarityto the text. In examples, the qualities used to describe text can besimilar to facets used to describe media content items. Then, the tracksare selected based at least in part on the quality. For instance, theword “blues” in the input text “now playing your blues playlist” can beidentified as a quality of the input text. Based on that quality, bluestracks can be selected.

In further examples, such as where the text input is from a virtualassistant, the text input is associated with a personality value (e.g.,inferred from the text input or expressly provided in conjunction withthe text input). In some embodiments, the personality value describes adesired personality with which to express the input text. Personalityvalues can reflect, for example, a happy, sad, aggressive, or laid-backpersonality among others. The personality value can be used to select aspeech synthesizer or parameters thereof, as well as to select tracks.

Traditional text-to-speech systems are designed to generate naturalsounding human speech. By contrast, certain examples herein can bedesigned to produce interesting or exciting output, even if the outputis unnatural. For instance, a listener would readily determine that theoutput of some embodiments herein was not the product of typical humanspeech because the output is the combination of audio from multiplesources (e.g., including a music track) but may nonetheless find theoutput exciting and interesting. In this manner, disclosed examples canproduce improved output (e.g., output that is more interesting orexciting) compared to traditional techniques.

In further examples, the audio snippet from the track need not actuallybe of a portion in the song where the lyrics are sung. For instance, theaudio snippet could instead be audio content that is evocative of theconcept expressed by the lyric. For instance, for the input text“playing your rock playlist”, the word “rock” could be replaced by aninstrumental audio snippet of a guitar riff or lick that is evocative ofrock music.

In an example, the text-to-speech system further includes a forcedalignment engine for aligning audio and lyrics of tracks. The forcedalignment engine receives a track's audio and the track's lyrics. Thenan acoustic model is selected based on the style of music of the track.The acoustic model is used to generate forced alignment data that alignsthe audio and lyrics of the track. The forced alignment data is added tothe forced alignment data store. Particular techniques can be applied totailor the forced alignment process to audio tracks (e.g., as opposed toregular speech). In an example, acoustic cues in the track are usedenhance alignment of lyrics to the audio, even in instances withoutmanual line boundaries. In another example, the acoustic model used toperform the forced alignment is trained for a particular type of music(e.g., specific artists or genres rather than entire datasets in orderto improve accuracy).

System Providing Text-to-Speech Functionality

FIG. 1 illustrates an example system 10 that provides audio output 14using a text-to-speech functionality. The system 10 has a user device100 and a server 150 connected over a network 190.

The user device 100 is a computing device, such as a handheldentertainment device, smartphone, tablet, watch, wearable device,in-dash vehicle head unit, an aftermarket vehicle media playbackappliance, a smart assistant device, a smart speaker, a smart homedevice, a television, a gaming console, a set-top box, a networkappliance, a media player, a stereo system, an Internet-of-thingsdevice, or a radio, among other devices or systems. The user device 100includes a user device memory 102, a user device processor 104, a userdevice interface 106, and a text-to-speech engine 110.

The user device memory 102 is one or a collection of components of theuser device 100 that stores data. The data can include computer-readableinstructions, data structures, program modules. The computer-readableinstructions can include instructions to perform one or more of theoperations described herein. Examples of user device memory 102 includetransitory or non-transitory computer-readable media (e.g., memoryaccessible by the user device processor 104). Examples of user devicememory 102 include memory based on magnetic-storage technology (e.g.,hard disk drives), optical-storage technology (e.g., optical discs),read-only memory technology (e.g., EEPROM memory), andrandom-access-memory technology (e.g., flash memory), among othertechnology. In some examples, the user device memory 102 encompassescomputer-readable communication media generally. Computer-readablecommunication media typically encodes data in a modulated signal (e.g.,a carrier wave) or other transport mechanism and includes anyinformation delivery media. The term “modulated data signal” refers to asignal that has one or more of its characteristics set or changed insuch a manner as to encode information in the signal. By way of example,computer-readable communication media includes wired media such as awired network or direct-wired connection, and wireless media such asacoustic, radio frequency, infrared, and other wireless media.Combinations of any of the above are also included within the scope ofcomputer-readable media. The user device memory 102 can be a transitoryor non-transitory computer-readable medium.

The user device processor 104 is one or more processing units, such ascentral processing units (CPU), digital signal processors, andfield-programmable gate arrays, among others. The user device processor104 is capable of executing instructions (e.g., instructions stored bythe user device memory 102) to cause performance of operations (such asthose described by processes herein).

The user device interface 106 is one or more components of the userdevice 100 by which the user device 100 can interact with the user oranother device. In some examples, the user device interface 106 includesa human-machine interface by which the user device 100 receives inputfrom or provides output to a user. For instance, the human-machineinterface can include: a touch-based user interface (e.g., a touchscreen for providing visual output to a user and receiving touch inputfrom a user), an utterance-based user interface (e.g., a microphone forreceiving voice input from a user and a speaker for providingsynthesized voice output to the user), a hardware-button-based userinterface (e.g., a hardware keyboard), a cursor-based user interface(e.g., a mouse or other pointing device), a tracking-based userinterface (e.g., tracking device that tracks a hand, finger, eye, orwand), other user interfaces, or combinations thereof, and the userdevice 100 plays a media content item based thereon. The user deviceinterface 106 can further include one or more components forcommunicating with another device, such as a wired (e.g., via Ethernet)or wireless (e.g., via a radiofrequency protocol, such as a cellular,BLUETOOTH, or WI-FI protocol) connection.

The user device interface 106 can further include a content outputdevice operative to provide audio output. Examples of the content outputdevice include a speaker assembly having one or more speakers, an audiooutput jack, a wireless transmitter (e.g., a BLUETOOTH transmitter), adisplay panel, and a video output jack. Other examples are possible aswell, such as transmitting a signal through the audio output jack orwireless transmitter to reproduce an audio signal by a connected orpaired device such as headphones, speaker system, or vehicle head unit.

The text-to-speech engine 110 converts text input into the audio output14. The audio output 14 can mimic a human speaking the text input. Asdescribed in examples herein, the audio output 14 can also include wordsand phrases are sung or rapped from one or more tracks. In still otherexamples, the audio output can include musical passages representativeof words or phrases. For instance, the text input may be “Now playingyour classic rock playlist” and a portion of the audio outputcorresponding to the text “classic rock” is instead a guitar riff from aclassic rock song. The text-to-speech engine 110 includes a combiningengine 112 and a speech synthesizer 114.

The combining engine 112 is component of the text-to-speech engine 110configured to provide audio output 14 that includes a combination ofaudio from multiple sources, such as a combination of synthesized speechaudio and an audio snippet from a track. In many examples, the combiningengine 112 controls selection of the audio from multiple sources forinclusion in the audio output 14. For instance, the combining engine 112can select the audio based on audio qualities or similarities amongaudio sources as described elsewhere herein. In other examples, thecombining engine 112 greedily joins the audio from multiple sources in apredefined manner (e.g., defined in a function call or based on audiometadata). The audio can be provided to the combining engine 112 fromanother component of the system 10, such as a component of thetext-to-speech engine 110 configured to select audio for combining withthe combining engine 112.

The speech synthesizer 114 is component that synthesizes speech. Thesynthesized speech is audio data designed to mimic audio of a humanspeaking text provided as input. The speech synthesizer 114 can beimplemented using any of a variety of techniques, such as byconcatenating segments of recorded speech or using formant synthesis.Implementations can include the use of deep learning or hidden Markovmodels. In the illustrated example, the speech synthesizer 114 islocated at the user device 100. In some examples, the server 150implements the speech synthesizer 114, and the user device 100cooperates with the server 150 to provide text input to and receiveaudio output from the speech synthesizer 114.

The server 150 is a computing device that provides services for othercomputing devices. In the illustrated example, the server 150 includescomponents that provide services to the user device 100 for operatingthe text-to-speech engine 110. In some examples, the server 150 isoperated or provided by a virtual assistant service. The server 150 canprovide other services. In some examples, the server 150 is operated orprovided by a subscription-based media streaming service to which a usermay have an account.

The server 150 includes a server processor 152, a server memory 154, aserver interface 156, a forced alignment data store 158, and a mediacontent data store 160. In some examples, the text-to-speech engine 110includes a forced alignment engine 116 and an acoustic model data store118. The server processor 152, the server memory 154, the serverinterface 156 are respectively processor, memory, and interfacecomponents of the server and can each share attributes with theircounterpart components of the user device 100. Although the figureillustrates the various components as being within a single server 150,they need not be. The various components can be spread across multiplevirtual or physical devices to provide the described capabilities.

The forced alignment engine 116 is an engine that produces forcedalignment data. In an example, the forced alignment engine 116 producesforced alignment data using the process shown in FIG. 3 (which isdescribed in more detail below). The forced alignment engine 116 canproduce the forced alignment data using an acoustic model, such as onestored in the acoustic model data store 118. An acoustic model is modeldescribing the relationship between the pronunciation of the lyrics(e.g., the phonemes thereof) and the audio itself. The acoustic modeldata store 118 is a data store that stores acoustic models. In examples,the acoustic model data store 118 stores a plurality of acoustic models.The plurality of acoustic models can include acoustic models that aregenerated for use with specific kinds of media content items (e.g.,tracks or podcasts), for use with specific genres of media content items(e.g., rock, blues, or rap), for use with specific artists, or for usewith specific kinds of vocalized lyrics (e.g., spoken, sung, or rapped),among others.

The forced alignment data store 158 is a data store that stores forcedalignment data. Forced alignment data is data regarding alignment oflyrics with the corresponding audio of the track where portions (e.g.,lines, phrases, words, syllables, or phonemes of the lyrics) of thelyrics occur. The forced alignment data typically expresses thealignment in terms of a time in the audio in which particular lyrics (orportions thereof) occur. An example of forced alignment data is shown inFIG. 4 (which described in more detail below). The forced alignment datacan be stored in any of a variety of formats, such as in TEXTGRID format(e.g., using the TEXTGRID research environment supported by DARIAH-DE).

The media content data store 160 is a data store that stores dataregarding media content items, such as tracks. In some examples, themedia content data store 160 stores data for each of a plurality ofmedia content items in a data structure (e.g., record of a table orother data structure) associated with each media content item. Anexample media content item data structure of the media content datastore 160 stores data regarding a particular media content item in oneor more fields, such as an ID field (e.g., storing an identifier of themedia content item data structure), a title field (e.g., storing a titleof the media content item data structure, such as a song title), acontent field (e.g., storing the content of the media content item or alink to the content of the media content item data structure, such asthe audio content of a song), and an audio fingerprint field. In someexamples, the media content item data structure further stores metadatafor the track. The media content item data structure can further storefacets of the media content item. The media content data store 160includes or is associated with a track data store 162 and a lyrics datastore 164. The track data store 162 is a data store that stores audio oftracks in a format suitable for storing media content. The lyrics datastore 164 is a data store that stores lyrics of media content items. Inan example, the lyrics data store 164 is a database that stores recordshaving lyric data.

The network 190 is an electronic communication network that supportscommunication between the user device 100 and the server 150. Anelectronic communication network includes a set of computing devices andlinks between the computing devices. The computing devices in thenetwork 190 use the links to enable communication among the computingdevices in the network. The network 190 can include components, such asrouters and other types of computing devices. In various examples, thenetwork 190 includes various types of links. For example, the network190 includes wired and wireless links. Furthermore, in various examples,the network 190 is implemented at various scales (e.g., as a local areanetwork or a wide area network, such as the internet).

In some examples the server 150 is or is part of a media-delivery systemthat streams, progressively downloads, or otherwise communicates music,other audio, video, or other forms of media content items to the userdevice 100 for later playback. The user device interface 106 can beconfigured to receive a user request to, for example, select mediacontent for playback on the user device 100.

Text-to-Speech Process

FIG. 2, which is made up of FIG. 2A and FIG. 2B, illustrates a process200 for generating audio output 14 based on input text 212. In anexample, one or more operations are provided by the text-to-speechengine 110, such as on the user device 100, server 150, or a combinationthereof. In the illustrated example, the process 200 begins withoperation 210.

Operation 210 includes obtaining the input text 212. The input text 212is text data that is to be used to generate the audio output 14. Theinput text 212 can be obtained in any of a variety of ways, such as froma program (e.g., a program operating on the user device 100 thatprovides virtual assistant functionality or accessibility services). Inan example, the text-to-speech engine 110 provides an ApplicationProgramming Interface (API) or otherwise exposing a function over whichinput text 212 can be received from another program. In still otherexamples, obtaining the input text 212 includes providing a userinterface via the user device interface 106 over which the input text212 can be received from a user. In further examples, the input text 212is obtained from a data store. Once obtained, the input text 212 can bestored in a data store, such as a database. Following operation 210, theflow moves to operation 220.

Operation 220 includes portioning the input text 212 into one or moresets 221. As illustrated, the sets 221 include a first text set 222, asecond text set 224, and in some examples a third text set 226 The sets221 can be stored in any appropriate data structure. In an example, thesets 221 are stored as arrays or lists of strings. In many examples, thesets 221 represent delineations of how text is to be processed in lateroperations. For instance, as described in relation to the process 200,the contents of the first text set 222 are converted into audio outputusing a first track and the contents of the second text set 224 areconverted into audio output using a speech synthesizer, and the contentsof the third text set 226 are converted into audio output using a secondtrack. The sets 221 may, but need not, include contiguous portions ofthe input text 212 (e.g., portions adjacent in the input text 212).Further, the contents of the sets 221 can be delineated in various ways,such as by phoneme, word, phrase, or sentence. Examples of input text212 and sets 221 are shown in the following tables I-III. Table I showsthe input text 212 split into three sets 221, with each of the sets 221including one element. Table II shows input text 212 split into threesets 221, with the first text set 222 including two elements that arenon-contiguous with respect to each other, the second text set 224including one element, and the third text set 226 being an empty set.Table III shows the first text set 222 and the third text set 226 beingempty and the second text set 224 including five elements with each wordof the input text 212 corresponding to one element.

TABLE I Overall Input Text “Now playing your jazz playlist” First textset {“Now playing your”} Second text set {“Jazz”} Third text set{“Playlist”}

TABLE II Overall Input Text “Now playing your jazz playlist” First textset {“Now playing your”, “playlist”} Second text set {“Jazz”} Third textset { }

TABLE III Overall Input Text “Now playing your pop playlist” First textset { } Second text set {“Now”, “playing”, “your”, “pop”, “playlist”}Second text set { }

In some examples, the input text 212 is pre-portioned such that theinput text 212 is obtained with markers delineating how the input text212 is to be portioned into sets or the input text 212 is provided asmultiple separate sets. In such examples, the text-to-speech engine 110can parse the input text 212 to determine whether the input text 212 isalready portioned and, if so, portion the input text 212 into differentsets.

In some examples, the input text 212 is obtained without the input text212 being pre-portioned. In such instances, the text-to-speech engine110 can portion the input text 212 using various techniques. In someexamples, there is a store of text data that the text-to-speech engine110 uses to portion the text. For instance, the store (e.g., adictionary data structure) defines key-value pairs that match text data(e.g., words, phrases, or types of content) with what kind of set thetext data should be placed. In an example, the store includes thekey-value pair {“rock”:1} indicating that where the word “rock” appearsin the input text 212, the word “rock” should be put into the first textset 222. In another example, the text-to-speech engine 110 uses anatural language processor to process the input text 212 and portion theinput text 212 into sets 221. In another example, a machine learningalgorithm (e.g., a neural network) that is trained to classify inputtext 212 processes the input text 212 data to portion it into sets 221.

The portioning can be based on various factors or parameters. In someexamples, the portioning includes identifying words or phrases that aresuited to being turned into audio output by taking a snippet from atrack (e.g., a song title where the song title is sung in a song, suchas “Panama” by Van Halen) and placing such words or phrases in acorresponding set. By contrast, certain words or phrases may be moresuited for being turned into audio output through use of a speechsynthesizer (e.g., certain error messages, such as “I'm sorry, Icouldn't find a track with that name”). Following operation, 220, insome examples the flow moves to operation 228. In other examples, theflow moves to operation 230.

Operation 228 includes determining a quality associated with the firsttext set 222. The quality 229 is an attribute of the first text set 222that is useful for identifying a track from which a snipped can beobtained that matches the first text set 222. For instance, the quality229 can be a music genre. The music genre can be detected by the genrebeing explicitly stated in the first text set 222 (e.g., the first textset 222 includes the name of a genre) or by being inferred by thecontent of the text set (e.g., the first text set 222 includes a name ofan artist or song associated with a genre). The quality 229 can be amusic artist. The music artist can be detected by the artist beingexplicitly stated in the first text set 222 (e.g., the first text set222 includes the name of the artist) or by being inferred by the contentof the text set (e.g., the first text set 222 includes a name of a trackassociated with an artist). In some examples, the quality 229 includes apersonality to be conveyed by the audio output 14. For instance, wherethe process 200 is performed in response to input text 212 from avirtual assistant having a specific personality (e.g., upbeat,soft-spoken, peppy, edgy, etc.), the quality 229 can describe thepersonality of the virtual assistant that is going to use the audiooutput 14. This can improve the ability of the virtual assistant tointeract with a user by preventing a jarring mismatch between thepersonality of the virtual assistant and the track used in conjunctionwith the first text set (e.g., it can be undesirable to have audiooutput for virtual assistant with a peppy cartoonish personality includea sample from a death metal song). In other examples, the quality 229 isa mood (e.g., happy or sad), a tempo (e.g., fast or slow), an era (e.g.,the 1970s), a region (e.g., Southern United States), or anotherattribute.

Operation 230 includes identifying a first track 232 having first tracklyrics 234 that include some or all of the elements of the first textset 222. In some examples, the identifying includes, for each element ofthe first text set 222, searching the media content data store 160(e.g., the lyrics data store 164 thereof) for tracks with lyricsincluding the element. In some examples, the searching is performedusing a lyrics provider service, such as by sending a request over anapplication programming interface of a lyrics provider.

In some examples, if no tracks are found, the flow moves back tooperation 220 to modify the first text set 222. The modifying can be toincrease the chance that a track is found. For instance, the modifyingcan include splitting elements of the first text set 222 that arephrases into shorter phrases or words. The modifying can also includeremoving words or phrases from the first text set 222. The modifying canalso include adding elements to the first text set 222 that were notthere before.

In some examples, if a plurality of tracks are found, then the firsttrack 232 can be selected from the plurality in any of a variety ofways. For instance, a track can be selected from the plurality at randomto be the first track 232. In other instances, the text-to-speech engine110 prompts a user (e.g., via the user device interface 106) or anotherprogram (e.g., the program requesting the audio output 14) to select atrack from the plurality of tracks. In such instances, the selectedtrack is the first track 232. In other instance, the plurality of tracksare filtered or sorted based a match between the tracks and the quality229. For instance, the quality 229 can be compared with facets oftracks. The first track 232 can then be selected based on the filteredor sorted tracks (e.g., the tracks are selected in descending order ofhow well each respective track matches the quality 229 and the top trackis selected). In still further instances, the tracks are sorted based ona user's taste profile or listening history, such that tracks that theuser enjoys listening to or that are frequently played for the user aremore likely to be selected as the first track 232. In addition, tracksthat are associated with the input text 212 can be selected as the firsttrack 232 over tracks that are not associated with the input text 212.For instance, where the input text 212 relates to a particular playlist(e.g., “now playing your summer fun playlist”) and a track from theparticular playlist has lyrics that include the first text set 222, thenthat track can be selected as the first track 232. In still furtherexamples, the tracks are sorted by their suitability for use inproducing the audio output 14 (e.g., based on how clearly the lyric isvocalized or how much background noise there is when the lyric isvocalized).

With the first track 232 selected, the flow moves to operation 240.

Operation 240 includes identifying a first audio location 242 of thefirst track 232 corresponding to the first text set 222 using forcedalignment data 400. For instance, the operation 240 includes identifyinga start time and an end time of the portion corresponding to the firsttext set 222 using the forced alignment data 400. In other examples, astart time and a duration is identified.

In examples, the first audio location 242 need not be limited to aportion where the lyric is vocalized. Instead, the first audio location242 can be set to logical boundaries (e.g., the beginning and end of alyrical or musical phrase) of a location in the track that contain thelyric. For instance, where the first text set 222 is the phrase “rockand roll” from the input text “now playing your rock and roll playlist”and the first track 232 can be identified as “Rock and Roll All Nite”,the first audio location 242 can be expanded to include the entirelyrical phrase “I wanna rock and roll all night” rather than just the“rock and roll” portion in order to preserve musical context and producean output that is less jarring to a person hearing the audio output. Theresulting audio output would then be “now playing your ‘I want to rockand roll all night’ playlist” rather than the verbatim “now playing yourrock and roll playlist”. Following operation 240, the flow moves tooperation 250.

Operation 250 includes creating a first audio snippet 252 from the firsttrack 232 that includes the first audio location 242. This operation 250includes extracting the first audio snippet 252 from the first audiolocation 242. It should be understood that where audio snippets areextracted from music tracks, the audio snippet can include additionalaudio beyond human vocal audio, such as the sound of one or moreinstruments. In some examples, the first track 232 is a special trackhaving isolated vocals of a song or other media content item. Inexamples, the operation 250 further includes fading the volume of thefirst audio snippet 252 in at the beginning of the first audio snippet252 and fading the volume of the first audio snippet 252 out at the endof the first audio snippet 252 to provide a smooth transition.

In some examples, operation 250 further includes operation 254.Operation 254 includes determining a suitability of the first audiosnippet 252. In some examples, determining the suitability includesdetermining how suitable the first audio snippet 252 is for use as partof a text-to-speech system. For instance, the suitability can includedetermining how clearly the lyrics of the first audio snippet 252 can beheard. In an example, the first audio snippet 252 is provided as inputto a speech-to-text system, and the resulting output is compared withthe lyrics of the first audio snippet. In an example, thecharacteristics of the audio of the first audio snippet 252 is analyzedto determine if the audio is suitable for use. In some examples, thereis a suitability threshold and, if the first audio snippet 252 does notsatisfy the suitability threshold, then the flow moves back to operation230 for selection of a different track as the first track 232. In someexamples, the first audio snippet 252 is processed to enhance theclarity of the speech (e.g., by modifying audio frequencies), and thesuitability of the processed first audio snippet 252 is checked again.

Following operation 250, the flow moves to operation 260.

Operation 260 includes creating one or more synthesized utterances 262based on the second text set 224. In an example, operation 260 includesproviding the second text set 224 as input to the speech synthesizer 114to produce one or more synthesized utterances 262. Following operation260, the flow moves to operation 280 (see FIG. 2B). In some examples,following operation 260, the flow moves to operation 264 (see FIG. 2B).

Operation 264 includes identifying a second track 266 having secondtrack lyrics 268. In some examples, identifying the second track 266 isthe same as or similar to the identifying the first track in operation230. In some examples, if no track is able to be identified as thesecond track 266, the flow moves to operation 220 where the input text212 is portioned into sets again. In other examples, if no track is ableto be identified as the second track 266, the flow moves to operation260 and the third text set 226 is used to create a synthesizedutterance.

In some examples, operation 264 further includes operation 270.Operation 270 includes selecting the second track 266 based onsimilarities in musical style with the first track 232. This can be usedto, for example, avoid an undesirable mismatch between the first track232 and the second track 266. For instance, using an audio snippet froman explicit rap track and an audio snippet from a children's song toform parts of a same audio output 14 can be undesirable and create apoor user experience. In some examples, where there is a plurality oftracks that have second track lyrics, the plurality of tracks can besorted by an amount of similarity between the facets of a given track ofthe plurality of tracks and the facets of the first track 232. In someexamples, the plurality of tracks are filtered based on the facets ofthe first track 232. In examples, the similarity is determined based oncomparing a distance (e.g., Euclidean distance or cosine distance)between the first track 232 and the second track 266 in a vector spacerepresentation of the first track 232 and the second track 266. Inexamples, determining the similarity of the first track 232 and thesecond track 266 includes applying one or more of the techniquesdescribed in U.S. Pat. No. 8,073,854, entitled “Determining thesimilarity of music using cultural and acoustic information”. If thetracks are sufficiently similar (e.g., the similarity satisfies asimilarity threshold), then the second track 266 can be used and theprocess 200 continues. Otherwise, a different track is selected as thesecond track 266.

Following operation 264, the flow moves to operation 272.

Operation 272 includes identifying a second audio location 274corresponding to the third text set 226. In some examples, operation 272can use the same or similar techniques to those described above inrelation to operation 240. Following operation 272, the flow moves tooperation 276.

Operation 276 includes creating a second audio snippet 278 including thesecond audio location 274. In some examples, operation 276 can use thesame or similar techniques to those described above in relation tooperation 250. Following operation 276, the flow moves to operation 280.

Operation 280 includes forming combined audio 282 by combining the firstaudio snippet 252, the second audio snippet 278 (when created), and thesynthesized utterance 262. This operation 280 includes concatenating thefirst audio snippet 252, the second audio snippet 278 (if exists) andthe synthesized utterance 262 together such that the resulting combinedaudio 282 corresponds to the input text 212. For instance, thisoperation 280 can include splitting or rearranging the audio to matchthe order in which the text occurs in the input text 212. Followingoperation 280, the flow moves to operation 290.

Operation 290 includes providing an audio output 14 that includes thecombined audio 282. This can include providing the audio output 14 asoutput via an audio output device of the user device 100. In someexamples where the operation 290 is performed by the server 150, theoperation 290 can include providing (e.g., streaming or making availablefor download) the audio output 14 to the user device 100.

Generating Forced Alignment Data

FIG. 3, illustrates a process 300 for creating forced alignment data fora track, such as the forced alignment data 400 used in operations 240and 272. The process 300 begins with operation 310.

Operation 310 includes receiving track audio 312 and track metadata 314for a track. In some examples, the track audio 312 is received from auser or a program (e.g., over an API) as an identifier of the trackaudio 312 (e.g., a unique identifier thereof) or a file path to thetrack audio 312. In some examples, the track audio 312 is obtained usingthe identifier or file path. In some examples, the track audio 312 isidentified by the location of the track audio 312 in the track datastore 162 and receiving the track audio 312 includes obtaining the trackaudio 312 from the track data store 162. In some examples, the trackaudio 312 itself is provided directly. The track metadata 314 can beobtained in a similar manner. For example, the track metadata 314 can bereceived from a user or a program as an identifier of metadata, anidentifier of the track (e.g., usable to look up the metadata in themedia content data store 160), or a path to a location storing metadata.In some examples, the metadata is provided directly. Following operation310, the flow moves to operation 320.

Operation 320 includes receiving lyrics 322 associated with the trackaudio 312. In an example, this includes obtaining the lyrics from thelyrics data store 164 using an identifier associated with the trackhaving the track audio 312. In examples, the identifier is defined inthe track metadata 314. In other examples, the lyrics 322 are obtainedfrom a third party data source that provides lyrics. Following operation320, the flow moves to operation 330.

Operation 330 includes obtaining an acoustic model 332. The acousticmodel 332 is a model describing the relationship between thepronunciation of the lyrics (e.g., the phonemes thereof) and the audioitself. In examples, there is a general acoustic model 332 that is usedfor the process 300. In some examples, the acoustic model 3232 is atriphone acoustic model trained on dictated speech (e.g., dictated booksfrom the LIBRIVOX collection of public domain audiobooks). While ageneral acoustic model 332 trained on general speech data (e.g.,dictated books) can be used, such an acoustic model 332 can havedecreased accuracy compared to acoustic models 332 trained on audio oftracks. The accuracy of the acoustic models 332 can be increased furtherby having a plurality of acoustic models 332 available for use, witheach of the acoustic models 332 being trained for use with particularkinds of track audio 312 (e.g., track audio 312 produced by particularmusical genres or artists). In such examples, obtaining the acousticmodel 332 includes selecting the acoustic model 332 from a plurality ofavailable acoustic models 332 using the track metadata 314. Forinstance, the acoustic models 332 can be stored in the acoustic modeldata store 118 in association with acoustic model metadata describingthe attributes (e.g., facets) of tracks used to produce the respectiveacoustic model 332. The attributes of the track audio 312 and theattributes used to train respective acoustic models 332 can be comparedand an acoustic model 332 that most closely matches the attributes ofthe track audio 312 can be selected. Following operation 330, the flowmoves to operation 340.

Operation 340 includes generating forced alignment data 400 using theacoustic model 332. In an example, generating the forced alignment data400 includes using an aligner to find a Viterbi path through the lyrics322 and the track audio 312 under the acoustic model 332. In an exampleFeature space Maximum Likelihood Linear Regression (fMLLR) is used. Forinstance fMLLR adaption of the acoustic model 332 to track audio 312 islearned. In an example, generating the forced alignment data 400includes generating the forced alignment data 400 on a line-by-linebasis (e.g., rather than aligning an entire track at once). Line-by-linealignment can speed up the alignment process. In other examples, thelyrics 322 are aligned without manual line boundaries and are insteadaligned using acoustic cues for pauses. In some examples, apronunciation dictionary (e.g., CMUDICT, the Carnegie Mellon UniversityPronouncing Dictionary) is used to determine pronunciation. For lyricsthat include of out-of-vocabulary words in lyrics, a pronunciationestimator can be used (e.g., PHONETISAURUS by Josef Novak). In someexamples, a forced alignment tool can be used to perform the alignment(e.g., the MONTREAL FORCED ALIGNER by McAuliffe et al.). Followingoperation 340, the flow moves to operation 350.

Operation 350 includes adding the forced alignment data 400 to theforced alignment data store 158. In some examples, an adapted acousticmodel is computed when the forced alignment data 400 is generated. Insuch examples, the adapted acoustic model can be stored in associationwith the forced alignment data 400. The forced alignment data 400 canthen be used as part of, for example, process 200 to produce audiooutput 14.

Forced Alignment Data

FIG. 4, illustrates an example visual representation of forced alignmentdata 400. In the illustrated example, the forced alignment data 400includes time data 410, audio data 420, and lyrics data 430. The audiodata 420 is visually represented as audio waveform data 422 and audiospectrogram data 424. The audio spectrogram data 424 includes pitch data426. The lyric data is illustrated as being represented as word lyricsdata 432, and phoneme lyrics data 434. The forced alignment data 400 isvisually represented in a manner that shows alignment among the datavertically. For example, as illustrated, the lyric “highway” begins inthe audio data 420 at time unit 9 and the word ends at approximatelytime unit 15. When implemented programmatically, the relationshipbetween the data can be expressed using any suitable data structure andneed not include all of the components illustrated in FIG. 4. In anexample, where the lyric “highway” is to be extracted from the trackhaving the audio data 420, the beginning and end of the word can bedetermined using the lyrics data 430 and the time data 410.

Example Use

FIG. 5 illustrates an example use of the system 10 to produce an audiooutput 14. In the illustrated example, the text-to-speech engine 110receives “now playing your heavy metal playlist” as input text 212 froma virtual assistant program operating on the user device 100 via afunction call. The text-to-speech engine 110 processes the input text212 and portions the input text 212 into a first text set 222 containing“heavy metal” and a second text set 224 containing “now playing your”and “playlist”. The second text set 224 is passed to the speechsynthesizer 114 to produce two synthesized utterances 262: onevocalizing the phrase “now playing your” and another vocalizing the word“playlist”.

The text-to-speech engine 110 identifies a track that contains the lyric“heavy metal” contained in the first text set 222 (e.g., the track “Bornto be Wild” is identified because it contains the lyric “heavy metal”).The portion of the track where the lyric is sung is identified using theforced alignment data 400 for the track, and the first audio location242 containing that lyric is extracted to form the first audio snippet252.

The synthesized utterances 262 and the first audio snippet 252 arecombined in the order in which their respective text appears in theinput text 212 to form the audio output 14: “now playing your heavymetal playlist”, where the phrase “heavy metal” is an audio snippet froma track rather than vocalized using a speech synthesizer and theremainder of the output is produced by the speech synthesizer 114. Theaudio output 14 is then output from the user device 100.

While various examples of the present invention have been describedabove, it should be understood that they have been presented by way ofexample, and not limitation. It will be apparent to persons skilled inthe relevant art(s) that various changes in form and detail can be madetherein. Thus, the present invention should not be limited by any of theabove described example embodiments, but should be defined only inaccordance with the following claims and their equivalents. Further, theAbstract is not intended to be limiting as to the scope of the exampleembodiments presented herein in any way. It is also to be understoodthat the procedures recited in the claims need not be performed in theorder presented.

Various operations and processes described herein can be performed bythe cooperation of two or more devices, systems, processes, orcombinations thereof.

It should be further understood that the term “text” is used forconvenience and may refer to, for example, alpha characters, numericcharacters, alphanumeric characters, American Standard Code forInformation Interchange (ASCII) characters, symbols, or foreign languageunicode (e.g., UTF-8).

The terms “computer-readable”, “machine-accessible medium” or“machine-readable medium” used herein shall include any medium that iscapable of storing, encoding, or transmitting a sequence of instructionsfor execution by the machine and that causes the machine to perform anyone of the methods described herein. Further, it is common in the art tospeak of software, in one form or another (e.g., program, procedure,process, application, module, unit, logic, and so on), as taking anaction or causing a result. Such expressions are merely a shorthand wayof stating that the execution of the software by a processing systemcauses the processor to perform an action to produce a result. Softwareexamples of the examples presented herein may be provided as a computerprogram product, or software, that may include an article of manufactureon a machine-accessible or machine-readable medium having instructions.

The invention claimed is:
 1. A system providing text-to-speechfunctionality, comprising: a forced alignment data store having storedthereon forced alignment data for tracks; a combining engine configuredto: obtain input text; portion the input text into a first text set, asecond text set, and a third text set; identify a first track havingfirst track lyrics that include the first text set; identify, using theforced alignment data, a first audio location of the first trackcorresponding to the first text set; create a first audio snippetcontaining the first audio location; identify a second track based onthe second track having second track lyrics containing the third textset; create a second audio snippet from the second track based on thethird text set; using a speech synthesizer, create a synthesizedutterance based on the second text set; combine the first audio snippet,the second audio snippet, and the synthesized utterance to form combinedaudio; and provide an audio output that includes the combined audio. 2.The system of claim 1, wherein the forced alignment data describesalignment between audio data of the tracks and lyrics data of thetracks.
 3. The system of claim 2, wherein the forced alignment data, foreach of the tracks, describes lyrics data and time data of where lyricsoccur in the audio data.
 4. The system of claim 1, wherein theidentifying the second track is further based on audio characteristicsof the first track and the second track.
 5. The system of claim 4,wherein identifying the second track includes: selecting the secondtrack based on similarities in musical style between the first track andthe second track.
 6. Then system of claim 5, wherein the similarities inmusical style between the first track and the second track is determinedbased on a distance between the first track and the second track in avector space.
 7. The system of claim 1, further comprising a forcedalignment engine for aligning input track audio and input track lyrics.8. The system of claim 7, wherein the forced alignment engine isconfigured to find a Viterbi path through the input track lyrics and theinput track audio under an acoustic model.
 9. The system of claim 7,wherein the forced alignment engine is configured to align the inputtrack lyrics and input track audio on a line-by-line basis.
 10. Thesystem of claim 7, wherein the forced alignment engine is configured to:receive a third track having track metadata; receive third track lyricsassociated with the third track; select an acoustic model from anacoustic model data store based on the track metadata; using theacoustic model, generate third-track forced alignment data that alignsaudio data of the third track and the third track lyrics; and add thethird-track forced alignment data to the forced alignment data store.11. The system of claim 1, wherein the combining engine is furtherconfigured to: determine a quality described in the input text, whereinidentifying the first track is based at least in part on the quality.12. The system of claim 11, wherein the quality is a music genre ormusic artist.
 13. A method comprising: obtaining input text; portioningthe input text into a first text set, a second text set, and a thirdtext set; determine a quality described in the first text set,identifying a first track based on: the first track having first tracklyrics that include the first text set; and the first track having thequality; identifying, using forced alignment data, a first audiolocation of the first track corresponding to the first text set;creating a first audio snippet containing the first audio location;identifying a second track based on the second track having second tracklyrics containing the third text set based on similarities in musicalstyle between the first track and the second track; creating a secondaudio snippet from the second track based on the second text set; usinga speech synthesizer, creating a synthesized utterance based on thesecond text set; combining the first audio snippet, the second audiosnippet, and the synthesized utterance to form combined audio; andproviding an audio output that includes the combined audio.
 14. A systemproviding text-to-speech functionality, comprising: a forced alignmentengine for aligning input track audio and input track lyrics, whereinthe forced alignment engine is configured to: receive a third trackhaving track metadata; receive third track lyrics associated with thethird track; select an acoustic model from an acoustic model data storebased on the track metadata; using the acoustic model, generatethird-track forced alignment data that aligns audio data of the thirdtrack and the third track lyrics; and add the third-track forcedalignment data to a forced alignment data store; the forced alignmentdata store having stored thereon forced alignment data for tracks; acombining engine configured to: obtain input text; portion the inputtext into a first text set and a second text set; identify a first trackhaving first track lyrics that include the first text set; identify,using the forced alignment data, a first audio location of the firsttrack corresponding to the first text set; create a first audio snippetcontaining the first audio location; using a speech synthesizer, createa synthesized utterance based on the second text set; combine the firstaudio snippet and the synthesized utterance to form combined audio; andprovide an audio output that includes the combined audio.
 15. The systemof claim 14, wherein the forced alignment data describes alignmentbetween audio data of the tracks and lyrics data of the tracks.
 16. Thesystem of claim 15, wherein the forced alignment data, for each of thetracks, describes lyrics data and time data of where lyrics occur in theaudio data.
 17. The system of claim 14, wherein the input text has athird text set; and wherein the combining engine is further configuredto: identify a second track based on the second track having secondtrack lyrics containing the third text set; and create a second audiosnippet from the second track based on the third text set, wherein thecombined audio further includes the second audio snippet.
 18. The systemof claim 17, wherein the identifying the second track is further basedon audio characteristics of the first track and the second track. 19.The system of claim 18, wherein identifying the second track includes:selecting the second track based on similarities in musical stylebetween the first track and the second track.
 20. Then system of claim19, wherein the similarities in musical style between the first trackand the second track is determined based on a distance between the firsttrack and the second track in a vector space.
 21. The system of claim14, wherein the forced alignment engine is configured to find a Viterbipath through the input track lyrics and the input track audio under anacoustic model.
 22. The system of claim 14, wherein the forced alignmentengine is configured to align the input track lyrics and input trackaudio on a line-by-line basis.
 23. The system of claim 14, wherein thecombining engine is further configured to: determine a quality describedin the input text, wherein identifying the first track is based at leastin part on the quality.
 24. The system of claim 23, wherein the qualityis a music genre or music artist.
 25. The method of claim 13, whereinthe forced alignment data describes alignment between audio data andlyrics data of tracks.
 26. The method of claim 25, wherein the forcedalignment data, for each of the tracks, describes lyrics data and timedata of where lyrics occur in the audio data.
 27. The method of claim13, wherein the identifying the second track is further based on audiocharacteristics of the first track and the second track.
 28. The methodof claim 27, wherein identifying the second track includes: selectingthe second track based on similarities in musical style between thefirst track and the second track.
 29. Then method of claim 28, whereinthe similarities in musical style between the first track and the secondtrack is determined based on a distance between the first track and thesecond track in a vector space.
 30. The method of claim 13, furthercomprising: using a forced alignment engine to find a Viterbi paththrough input track lyrics and input track audio under an acousticmodel.
 31. The method of claim 13, further comprising: using a forcedalignment engine to align input track lyrics and input track audio on aline-by-line basis.
 32. The method of claim 13, further comprising: witha forced alignment engine: receiving a third track having trackmetadata; receiving third track lyrics associated with the third track;selecting an acoustic model from an acoustic model data store based onthe track metadata; with the acoustic model, generating third-trackforced alignment data that aligns audio data of the third track and thethird track lyrics; and adding the third-track forced alignment data toa forced alignment data store.
 33. The method of claim 13, furthercomprising: determining a quality described in the input text, whereinidentifying the first track is based at least in part on the quality.34. The method of claim 33, wherein the quality is a music genre ormusic artist.
 35. A method comprising: with a forced alignment enginefor aligning input track audio and input track lyrics: receiving a thirdtrack having track metadata; receiving third track lyrics associatedwith the third track; selecting an acoustic model from an acoustic modeldata store based on the track metadata; using the acoustic model,generating third-track forced alignment data that aligns audio data ofthe third track and the third track lyrics; and adding the third-trackforced alignment data to the forced alignment data store obtaining inputtext; portioning the input text into a first text set a second text set;determine a quality described in the first text set, identifying a firsttrack based on: the first track having first track lyrics that includethe first text set; and the first track having the quality; identifying,using forced alignment data, a first audio location of the first trackcorresponding to the first text set; creating a first audio snippetcontaining the first audio location; using a speech synthesizer,creating a synthesized utterance based on the second text set; combiningthe first audio snippet and the synthesized utterance to form combinedaudio; and providing an audio output that includes the combined audio.36. The method of claim 35, wherein the forced alignment data describesalignment between audio data and lyrics data of tracks.
 37. The methodof claim 36, wherein the forced alignment data, for each of the tracks,describes lyrics data and time data of where lyrics occur in the audiodata.
 38. The method of 35, further comprising: identifying a secondtrack based on audio characteristics of the first track and the secondtrack, wherein the combined audio includes a second audio snipped fromthe second track.
 39. The method of claim 38, wherein identifying thesecond track includes: selecting the second track based on similaritiesin musical style between the first track and the second track.
 40. Thenmethod of claim 39, wherein the similarities in musical style betweenthe first track and the second track is determined based on a distancebetween the first track and the second track in a vector space.
 41. Themethod of claim 35, further comprising: with the forced alignmentengine, finding a Viterbi path through input track lyrics and inputtrack audio under an acoustic model.
 42. The method of claim 35, furthercomprising: with the forced alignment engine, aligning input tracklyrics and input track audio on a line-by-line basis.
 43. The method ofclaim 35, further comprising: determining a quality described in theinput text, wherein identifying the first track is based at least inpart on the quality.
 44. The method of claim 43, wherein the quality isa music genre or music artist.